For systems that do not have a posix shell.
* configure.ac (GUILE_TOOLS_EXE): new conditional
* libguile/Makefile.am (guile-tools)[GUILE_TOOLS_EXE]: new binary target
* libguile/guile-tools.c: new file
* meta/Makefile.am (guile.scm): new data
[!GUILE_TOOLS_EXE](install-exec-hook): don't alias guile-tools to guild
(CLEANFILES): add guild.exe
